Shear bond strengths of orthodontic brackets cemented to bovine enamel with composite and resin-modified glass ionomer cements.

PURPOSE The purpose of this in vitro study was to determine the effects of short- and long-term storage on the shear bond strength of metal, polycarbonate, and ceramic orthodontic bracket bases using autopolymerizing resin composite and resin-modified glass ionomer cements (RMGIC). The glass ionomer cement was applied in both a wet and a dry environment. METHODS With a method developed in the authors' laboratory, orthodontic brackets were cemented under constant pressure to embedded bovine incisor enamel. All cements were mixed and applied in accordance with the manufacturer's instructions. The specimens were stored in water at 37 degrees C for 24 hours, 7 days, or 180 days. After the lapse of each time interval, they were shear tested to failure. The shear bond strengths (SBSs) were converted to megapascals (MPa). An adhesive remnant index (ARI) was used to record the site of the residual cement. RESULTS There were no precipitous increases or decreases in SBS over a lapsed time of 180 days, although some variations occurred between 24 hours and 7 days. Similar findings were recorded for ARI. CONCLUSIONS The bracket base-cement combinations produce clinically sustainable SBSs over time. Selection of the cement may be important in patients who exhibit a high risk for caries.